Buy-to-Let Mortgages Explained: A Guide for UK Landlords

A buy-to-let mortgage is a loan for buying a property you intend to rent out rather than live in — and it works quite differently from the mortgage on your own home. Lenders assess it mainly on the rent the property can earn, not just your salary. Deposits are typically larger, interest-only is the norm, and a layer of stress testing checks the numbers still work if rates rise.

If you’re weighing up your first rental property — or adding to the ones you already own — this guide walks through how these mortgages work, what lenders look for, and the considerations that catch landlords out. For the specifics, our buy-to-let mortgage service is what we do day in, day out.

How is a buy-to-let mortgage different from a residential mortgage?

Four things set buy-to-let apart from the mortgage on your own home:

The rent does the heavy lifting. With a residential mortgage, the lender asks whether your income covers the payments. With buy-to-let, the first question is whether the rent covers them — with room to spare (more on that below). Your personal income still matters, but it’s a supporting act rather than the headline.

Deposits are typically larger. Most buy-to-let lenders want a deposit of around 25% of the property’s value, though some will accept 20%. So on a £400,000 property, you’d typically need a £100,000 deposit, with the lender providing the remaining £300,000. Residential deposits can be as low as 5–10%, so the upfront commitment is one of buy-to-let’s biggest hurdles.

Interest-only is the norm. Most buy-to-let mortgages are interest-only: you pay just the interest each month, and the original loan is still owed in full at the end of the term. That keeps monthly payments lower — which helps the rental sums stack up — but you need a credible plan for repaying the capital, whether that’s selling, remortgaging, or other funds. Repayment buy-to-let mortgages exist too — they cost more each month, but you owe less over time.

Rates tend to be a little higher. Lenders price buy-to-let as business lending, so rates generally sit somewhat above equivalent residential deals. You’ll still choose between fixed rates and variable or tracker rates that move with the Bank of England base rate.

What are the benefits of buying to let?

There are good reasons buy-to-let has remained popular with investors:

• Rental income. A tenanted property generates a regular monthly income — and if that income comfortably exceeds your mortgage payment and running costs, the surplus is yours (before tax).
• Potential for capital growth. UK property values have grown significantly over the long term, and many landlords invest with one eye on what the property might be worth in ten or twenty years. But be honest: past growth is no guarantee of future growth, and values can fall as well as rise.
• Strong rental demand. More people are renting, and renting for longer, than in previous generations. In areas with healthy tenant demand, a good rental property shouldn’t sit empty for long.

None of these benefits is automatic. They depend on buying the right property at the right price, keeping it let, and managing costs — which is why we’d suggest reading our guide on how to choose the right investment property before you start viewing.

Am I eligible for a buy-to-let mortgage?

Criteria vary between lenders — one reason a broker earns their keep — but most look for:

• Age 21 or over. Most lenders set a minimum age of 21, and many set maximum ages for the end of the mortgage term.
• A deposit of around 20–25%. As above, 25% is typical; a handful of lenders accept 20%.
• A good credit history. A patchy record doesn’t always rule you out, but it narrows the field and can mean higher rates.
• A solid income of your own. Even though the rent drives the affordability calculation, many lenders want to see a minimum personal income — reassurance that you could cover the mortgage during gaps between tenants.
• The rental numbers stacking up. The expected rent has to clear the lender’s coverage requirements (see the stress test section below). A valuer will assess what the property should realistically let for locally — and if similar properties nearby are sitting unlet, that can affect their view.

First-time landlord or growing a portfolio — does it change anything?

It does, in a few practical ways.

If this is your first rental property, some lenders will want you to already own your own home, and a few are cautious about first-time buyers going straight into buy-to-let. Plenty do cater for first-time landlords — matching you to the right ones is where searching across over 100 lenders, rather than walking into one bank, makes a real difference.

If you’re building a portfolio, the rules shift again. Once you own four or more mortgaged buy-to-lets, lenders generally class you as a “portfolio landlord” and look at your whole portfolio when you apply for the next purchase — not just the property in front of them. It’s more paperwork, but a well-organised portfolio with sensible borrowing across it shouldn’t struggle.

Should I buy in my own name or through a limited company?

One of the most common questions we’re asked — and the honest answer is that it’s two questions wearing one coat.

The mortgage question is ours. Personal buy-to-let and limited company buy-to-let are different lending markets, with different lenders, products and criteria. We can find you an option for either route and tell you how the borrowing compares.

The tax question is one for your accountant. Whether a limited company structure leaves you better or worse off depends on your income, your other properties, your long-term plans and how profits are taken — that’s tax advice, and not something a mortgage adviser should decide for you. What we will do is work alongside your accountant: once you’ve taken their advice on structure, we’ll find the lending to match it. If you don’t have an accountant yet, have that conversation before you offer on a property.

How do lenders stress test a buy-to-let mortgage?

This is the bit of buy-to-let underwriting that surprises people most, so it’s worth understanding before you fall in love with a property.

Lenders don’t just check that the rent covers the mortgage payment — they want it covered with a margin, and at a higher interest rate than you’ll actually pay. Two things drive this:

• The interest cover ratio (ICR). Most lenders require the expected rental income to be at least 125% of the mortgage payment, and some set the bar higher depending on your circumstances, including your tax band. A property where the rent only just covers the payment generally won’t pass.
• The stressed rate. Rather than testing the rent against your actual product rate, lenders typically test it against a higher notional rate — checking the deal would still work if rates rose.

Two useful wrinkles: some lenders relax their ICR requirements if you have a strong personal income, and the rental figure used is the valuer’s view of achievable rent, not the number on the listing. This is why two lenders can look at the same property and offer very different maximum loans — and why it pays to compare lenders’ rental calculations rather than trying one bank and hoping.

To get a feel for the payment side of the sums, our mortgage repayment calculator is a good place to start.

What costs do landlords forget to budget for?

The mortgage payment is only the beginning. Thriving landlords budget conservatively for everything else:

• Void periods. There will be times when the property is empty and no rent is coming in — between tenancies, during refurbishments, or in a slow market. The mortgage still needs paying, so keep a cash buffer rather than relying on every month being let.
• Stamp duty. Buy-to-let purchases usually attract a stamp duty surcharge on top of the standard rates for additional properties — a meaningful sum to factor in from day one.
• Tax on your rental income. Rent is taxable and needs declaring on your self-assessment tax return — and landlord reporting requirements are changing, with quarterly digital tax reporting on the way for many landlords.
• Capital gains tax. If you sell at a profit down the line, capital gains tax will likely be due. Accountant territory, but it belongs in your long-term sums.
• Maintenance and repairs. Boilers fail, roofs leak, and as the owner those bills are yours. Older properties especially need a realistic annual maintenance budget.
• Letting and management fees. If an agent finds your tenants or manages the property, their fees come off the top.
• Landlord insurance. Standard home insurance won’t cover a rental property — you’ll need a landlord policy.
• Energy efficiency upgrades. Rules on minimum EPC ratings for rentals are tightening, and bringing an older property up to standard can be a significant outlay — see what the EPC deadline could mean for landlords.
• Interest rate movements. If you’re on a variable rate — or when your fixed deal ends — a rise in rates feeds straight into your costs. Stress test your own numbers the way the lender does.

What are my legal responsibilities as a landlord?

Owning a rental property comes with legal duties — not optional extras. The headline ones:

• Gas safety. Under the Gas Safety (Installation and Use) Regulations 1998, gas appliances, pipework and flues must be safely maintained, with an annual inspection. You must keep a Gas Safety Record, give a copy to your tenant at the start of the tenancy, and repair faulty equipment promptly once reported.
• Electrical safety. Electrical installations and appliances supplied with the property must be safe, with regular checks for defects — annual checks are widely recommended — and anything unsafe removed before letting.
• Furniture and furnishings. Under the Furniture and Furnishings (Fire) (Safety) Regulations 1993, most furniture you provide must carry the appropriate fire-resistance labels.
• Smoke alarms. Working smoke alarms need to be installed and maintained.

Beyond safety, the wider legal landscape is shifting — tenancy law is going through its biggest shake-up in a generation, so staying informed (or using a letting agent who is) matters more than ever.

How do I grow a portfolio responsibly?

If the first property works, the natural question is how to fund the second. A few principles we’d encourage:

• Let equity do some of the work — carefully. As a property’s value grows, remortgaging can release equity towards the next deposit. It’s how many portfolios are built, but it increases the borrowing secured on the first property — so the rent still needs to cover the larger loan with margin.
• Buy on numbers, not emotion. Every additional property should pass the same conservative tests as the first: realistic rent, realistic costs, a margin for voids and rate rises. If the figures only work when everything goes right, walk away.
• Review at every deal end. When a fixed rate finishes, don’t drift onto the lender’s standard variable rate — that eats straight into your rental profit. A deal ending is also the natural moment to reassess rent, value and structure.
• Keep your buffer growing with the portfolio. One empty property is an annoyance; two at once on thin reserves is a crisis. Scale your cash cushion as you scale your borrowing.
• Plan the long game. Think about how long you’ll hold each property, what happens at the end of each mortgage term — particularly for interest-only loans, where the capital falls due — and what your eventual exit looks like.

Buy-to-let mortgage FAQs

How much deposit do I need for a buy-to-let mortgage?

Typically around 25% of the property’s value, though some lenders accept 20%. A bigger deposit means a lower loan-to-value ratio, which generally unlocks better rates.

Can I get a buy-to-let mortgage as a first-time buyer?

Some lenders will consider it, but the field is narrower — many prefer applicants who already own their own home, and the affordability assessment tends to be more cautious. Far from impossible; it just makes choosing the right lender more important.

Is interest-only or repayment better for buy-to-let?

Neither is “better” — they suit different plans. Interest-only keeps monthly payments lower and is the most common choice for landlords, but the full loan remains owing at the end of the term, so you need a clear repayment strategy. A repayment mortgage costs more each month but steadily reduces what you owe.

Do I pay tax on rental income?

Yes — rental income must be declared on your self-assessment tax return, and other taxes (stamp duty when you buy, potentially capital gains tax when you sell) apply too. How much, and how best to structure things, is one for your accountant — we’ll work alongside them on the mortgage side.

What happens if my property has no tenants?

The mortgage payments continue whether or not rent is coming in, which is why every landlord needs a cash reserve for void periods. Lenders think the same way — it’s one reason many like to see a personal income behind the application.

How many buy-to-let mortgages can I have?

There’s no universal limit, but once you have four or more mortgaged buy-to-lets, lenders treat you as a portfolio landlord and assess your whole portfolio when you apply for more borrowing. Some individual lenders cap how many properties they’ll fund for one borrower — another reason a wide choice of lenders helps as you grow.

Talk it through with a human

Buy-to-let rewards careful planning, and the lending side is genuinely complicated — rental calculations, stress tests and criteria vary widely from lender to lender. That’s where we come in: we search over 100 lenders and thousands of deals to find an option that fits your property, your plans and the way you’re holding it.

Book a no-obligation chat and we’ll talk through your plans, run the numbers honestly, and tell you what’s realistic — including, sometimes, “not yet”.

There may be a fee for mortgage advice. The precise amount will depend upon your circumstances.

Your home/property may be repossessed if you do not keep up repayments on a mortgage or other debt secured on it.

Some buy to let mortgages are not regulated by the Financial Conduct Authority.

All the information in this article is correct as of the date of its last update (11th June 2026). The information provided in this article, including text, graphics and images does not, and is not intended to, substitute advice; instead, all information, content, and materials available in this article are for general informational purposes only. This article does not constitute tax advice — speak to a qualified accountant about your own position.